Miniature transformer



April 30, 1968 R. A. FULLER 3,331,251

MINIATURE TRANSFORMER Filed July 1966 2 Sheets-Sheet 1 HGQ3G. FEGQBb.

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INVENTOR Robert A. Fuller saZZZj By M E ATTORNEYS April 30, 1968 R. A. FULLER 3,381,251

MINIATURE TRANSFORMER Filed July 5. 1966 2 Sheets-Sheet 2 I00 I20 I30 /lOo U f H] A FIG.I3A.- FIG.

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INVENTOR Robert A. Fuller BY %/LL:M7/

ATTORNEYS United States Patent 3,381,251 MINIATURE TRANSFORMER Robert A. Fuller, 501 W. 10th St, Mount Carmel, llll. 62863 Continuation-impart of application Ser. No. 305,375, Aug. 29, 1963. This application July 5, 1966, Ser. No. 564,504

7 Claims. (Cl. 336-83) ABSTRACT OF THE DISCLOSURE A miniature transformer having a core and circular end flanges attached thereon by swaging. A sleeve surrounds the core and end flanges and forms an air gap with the end flanges.

This invention relates to transformers and more particularly to miniature transformers and is a continuation-inpart of prior co-pending application Ser. No. 305,375, filed Aug. 29, 1963, and now abandoned.

It is an object of this invention to provide a miniature transformer having a novel core structure.

It is another object of this invention to provide a miniature transformer having a novel core structure which results in a decreased Foucault and eddy currents therein.

Another object of this invention is to provide a miniatransformer having a novel core structure including a spool, a sleeve external to the spool and a bonding medium maintaining a predetermined gap between said spool and said sleeve.

Still another object of this invention is to provide a miniature transformer having a new and novel structure facilitating the extension of winding leads therefrom.

Another object of the invention is to provide a miniature transformer having a new and novel split core and split sleeve structure, whereby the external winding leads of the said transformer may be peripherally disposed thereon.

These and other objects of this invention will become more fully apparent with reference to the following specification and drawings which relate to several preferred embodiments of the invention.

In the drawings:

FIGURE 1 is a side elevation of the main spool portion of the core of the invention;

FIGURE 2 is an end view of FIGURE 1;

FIGURE 3a is a front elevation of an end flange or washer member of the core of the invention;

FIGURE 3b is a side elevation of FIGURE 30;

' FIGURE 4a is a front elevation of another embodiment of end flange or washer member of the core of the invention;

FIGURE 4b is a side elevation of FIGURE 4a;

FIGURE 5a is a side elevation of a sleeve member of the present invention;

FIGURE 5b is an end view of FIGURE 50;

FIGURE 6a is a side elevation of one embodiment of a complete spool assembly of the core of the invention;

FIGURE 6b is an end view of FIGURE 6a;

FIGURE 7a is a side elevation of another embodiment of a complete spool assembly of the core of the invention;

FIGURE 7b is an end view of FIGURE 7a;

FIGURE 8a is a side elevation of a completed transformer of the present invention;

FIGURE 8b is an end view of FIGURE 8w;

FIGURE 9 is a side elevation of a miniature transformer at an intermediate stage of the process of manufacture;

FIGURE 10 is an end view of FIGURE 9;

FIGURE 11 is a side elevation of apparatus and operation in the manufacture of miniature transformers under the present invention;

FIGURE 12 is an end view of FIGURE 11;

FIGURE 13a is a side elevation of another embodiment of the spool assembly of the present invention;

FIGURE 13b is an end view of the embodiment of FIG- URE 1311;

FIGURE 14a is a side elevation of another embodiment of the sleeve member of the present invention;

FIGURE 14b is an end view of the embodiment of FIG- URE 14;

FIGURE 15a is a side elevation of another embodiment of a completed transformer of the present invention incorporating the features of FIGURES 13a, b and 14a, b of the present invention; and

FIGURE 15b is an end view of the embodiment of FIGURE 15a.

Referring in detail to the drawings, and more particularly to FIGURES 1, 2, 3, 4, 6 and 7 the transformer core 10 is shown as including a body portion 12 which is cylindrical in shape and has reduced radius peripheral end shoulders 14. The end shoulders 14 are dimensioned to a substantially close fit internally of the axial bores 16 and 18, respectively, in first and second end washers or flanges 20 and 22, which, together with the body portion 12, give the core 10 the shape of a spool or the like.

The second end flanges 22 are provided with a radial slot 24, extending from the bore 18 to the periphery thereof, for a purpose to be hereinafter described.

The body portion 12 of the core 10 is alternatively provided with or without a central bore 26, as shown, respectively, in FIGURES 6 and 7.

As shown in FIGURE 6, the core 10 may include laminated sets of first and second end flanges 20 and 22, respectively, which results in a reduction of Foucault current from the level of the embodiment of FIGURE 7. The latter embodiment uses single end flanges.

In both of the above cases, the end flanges 20 and 22 are held on the shoulders 14 either by swaging or by a suitable potting compound. A further alternative is a friction fit which is less desirable because of the rigid tolerances involved.

Once the core 10 has been assembled to the condition of FIGURES 6 and 7, all the surfaces thereof are polished to a very smooth finish and the core 10 is subsequently hydrogen annealed to develop optimum magnetic qualities.

After annealing, suitable transformer windings (not shown) are wound on the body portion 12 of the core 10 between the first and second end flanges 20 and 22. The start and finish ends of the windings are extended externally of the core 10 by passing therethrough the radial slot 24 in the second end flange 22.

Referring now to FIGURES 5, 9 and 10, a cylindrical sleeve 28 having a contiguous radial slot 30 therein and a bore 32 with a diameter slightly greater than the outer diameters of the first and second end flanges 20 and 22 is telescoped over the core 10. The sleeve 28 is substantially the same length as the core 10.

All of the components of the core 10 and sleeve 28 comprise high permeability nickel-iron alloy.

At this point, eddy and Foucault currents are effectively precluded in the core 10 by the gap between the flanges 20 and 22 and their respective shoulders 14, the sleeve slot 30, and the gap 34 between the outer periphery of the said end flanges 20 and 22 and the inner periphery of the sleeve 28 (i.e. the wall of the bore 32).

The use of the core structure 10 of FIGURE 6 provides additional gaps 36 and 38 between the multiple end flanges 20 and 22, respectively.

Referring additionally to FIGURES 11 and 12, a

clamping means 40 and test circuit 42 are provided whereby the inductance of the transformer windings may be selectively adjusted.

The clamp 49 comprises first and second adjacent die-bars or blocks 44 and 46, respectively, having opposed, substantially semi-circular first and second mold cavities 48 and 50 therein, respectively. The die-bars 44 and 46 are held together by thumb screws 52 spaced apart in any desired amount for optimum pressure adjustment along the length of the said die-bars.

As also shown in FIGURES 9 and 10, the transformer lead wires 54 are brought out of the end of the transformers T containing the radial slot 24. The test circuit 42 includes the leads 54 and a metering means 56 selectively coupled with the windings 54 via a switch or the like 58, whereby the inductance of the windings may be determined.

Just before the transformers T are placed in the mold cavities 48 and 50 of the clamping means 49, any suitable potting compound is placed in the sleeve gap 36.

The inductance of the transformer windings is adjusted by varying the sleeve-flange gap 34 by the selective application of clamping pressure via die-bars 4446 and thumb-screws 52. The desired inductance is indicated on the meter means 56 when the proper clamping pressure has been applied.

The suitable potting compound may then be cured in an oven or the like (not shown) while still in the clamp to effect full adherence to the sleeve 28 at the radial slot 30 and thus set the gap 34- in its adjusted dimension.

Subsequently, a potting compound forming base 60 is molded on one end of the transformer T adjacent the first end flange 20 and a potting compound 62 is effected around the lead wires 54 adjacent the second and slotted end flange 22.

Finally, the entire transformer T, as shown in FIG- URES 8 and 8a, is encapsulated in a coating of potting compound.

With specific reference to FIGURES 13a, 13b, 14a, 14b, 15a and 15b, there is illustrated another embodiment of the invention. This form comprises a novel split core a formed of sections 12a and 13a and a split sleeve 28a formed of half-sections 30a and 31a.

When assembling the core sections and sleeve sections the winding leads 54a from the core 10a may be peripherally disposed between the opposed edge-s 32a and 33a of the respective split sleeve sections 30a and 31a, see FIGURES a and 15b.

By dividing core 10a, into a plurality of juxtaposed longitudinal sections, for example, two or more pieces 12a and 13a, two or more pieces as shown in FIGURES 13a and 13b in the provision of a longitudinally laminated structure further extension of the laminated structure is provided and the Foucault currents are further reduced. Also, as in FIGURES 14a and 1412 providing further extensions of the laminated structure with respect to FIGURES 5a and 5b by dividing the sleeve 28a into two or more sections a and 31a Foucault currents are further reduced and the leads 54a of the assembled miniature transformers may lead off on the periphery of the core, see FIGURES 15a and 15b, rather than from the center as in the first illustrated embodiments, see FIGURES 8a and 9.

The split core sections and the enshrouding sleeve sections with the leads 54a from the core windings, when assembled may be potted with any suitable potting compound 62a, see FIGURE 15a.

Prior art devices have required that radial sleeve-slots be lined up with radial slots in the end flanges of the core, but because of the new and novel core structure of the present invention this is no longer a necessary core parameter.

In addition, the tedious nature of prior manufacturing techniques requiring such practices as forging unitary core shapes or milling unitary core shapesand the addi- 4 tional slotting and loss compensating operations thereon have been eliminated by the present invention.

Thus, it can be seen from the foregoing specification and drawings that this invention solves a series of longfelt problems in the art.

It is to be understood that the several embodiments shown and described herein are for the purpose of example only and are not intended to limit the scope of the appended claims.

What is claimed is:

1. A miniature transformer comprising a core having a cylindrical body portion with peripheral end shoulders of a different radius than said body portion, and circular end flanges on said shoulders maintained thereon by swaging said body portion; windings on said core; a cylindrical sleeve coextensive with said core externally of said windings and immediately adjacent and substantially concentric with said end flanges to form an air gap therebetween, said sleeve including a contiguous radial slot means; and potting means in said slot to set said slot means in a predetermined width, whereby said sleeve is constrained to provide a desired air gap size with said end flanges, said end flanges comprising multiple laminations on each end of said body portion of said core.

2. A miniature transformer comprising a longitudinally laminated core, a winding on said core, a longitudinally laminated sleeve co-extensive with said core and exterior of said winding on the core, and leads from said winding extending peripherally of the said laminated sleeve, said respective core and said sleeve co-extensive therewith being joined together with suitable potting means.

3. A miniature transformer comp-rising a split core having a plurality of sections to form a laminated cylindrical body portion, said laminated body portion having peripheral end shoulders of a different radius than said laminated body portion, windings on said core, a split cylindrical sleeve having a plurality of sections to form a laminated sleeve, said laminated sleeve being coextensive with said core externally of the core windings, external winding leads from the core windings, peripherally disposed along the said laminated sleeve, and a potting compound for maintaining said core, said sleeve and said lead windings in proper position to promote reduction of the Foucault currents. V 4. A miniature transformer comprising a core having a cylindrical body portion with peripheral end shoulders of a different radius than said body portion, and circular end flanges on said shoulders maintained thereon by swaging said body portion; windings on said core; a cylindrical sleeve coextensive with said core externally of said windings and immediately adjacent and substantially concentric with said end flanges to form an air gap therebetween, said sleeve including a contiguous radial slot means forcibly variable during assembly of the core and sleeve; said end flanges at one end of said core having a radial slot means therein for passing leads to and from said windings; and potting means on said transformer immobilizing said leads and providing an external sealed sheath on said transformer to secure the said core and sleeve in the fixed potted relation to form a predetermined air gap therebetwcen for desired value of inductance; said end flanges comprising multiple laminations on each end of said body portion of said core.

5. A miniature transformer comprising a core having a cylindrical body portion with peripheral end shoulders of a different radiusthan said body portion, and circular end flanges on said shoulders maintained thereon by swaging said body portion; windings on said core; a cylindrical sleeve coextensive with said core externally of said windings and immediately adjacent and substantially concentric with said end flanges to form an air gap therebetween; and potting means joining said core and said sleeve; the core comprising a plurality of juxtaposed longitudinal sections in the provision of a longitudinally laminated core.

6. A miniature transformer comprising a core having a cylindrical body portion with peripheral end shoulders of a different radius than said body portion, and circular end flanges on said shoulders maintained thereon by swaging said body portion; windings on said core; a cylindrical sleeve coextensive with said core externally of said windings and immediately adjacent and substantially concentric with said end flanges to form an air gap therebetween; and potting means joining said core and said sleeve; the sleeve comprising a plurality of juxtaposed 10 longitudinal sections in the provision of a longitudinally laminated sleeve.

7. A miniature transformer comprising a core having a cylindrical body portion with peripheral end shoulders centric with said end flanges to form an air gap therebetween; and potting means joining said core and said sleeve; said core and said sleeve each forming a plurality of juxtaposed longitudinal sections in the provision of a 5 longitudinally laminated unit.

References Cited UNITED STATES PATENTS 1,673,062 6/1928 Davis 336-83 2,949,591 8/1960 Craige 33683 FOREIGN PATENTS 474,035 5/1951 Canada.

of a different radius than said body portion, and circular 15 LARAMIE ASKIN, primary Examiner end flanges on said shoulders maintained thereon by swagiig said body portion; windings on said core; a cylindrical sleeve coextensive with said core externally of said windings and immediately adjacent and substantially con- LEWIS H. MYERS, Examiner.

D. A. TONE, Assistant Examiner. 

